David Simon was right at home on stage at the National Portrait Gallery, moderating a post-screening panel of people who made the film "Spotlight" happen.

"I'm going to start with the artifice of the film. As a newspaper reporter for 13 years, this was porn — in the best possible way," said the former scribe for the Baltimore Sun and creative force behind HBO's "The Wire," "Treme" and "Show Me a Hero."

The crowd that gathered for Wednesday' night's opening of Double Exposure: The Investigative Film Festival roared in approval. For an auditorium filled with journalists or the people who love them, the movie and its story was a celebration of journalism at its best: The Boston Globe's Pulitzer-Prize winning series about serial sexual abuse and the cover-up in the Catholic Church. Simon's panel — which discussed everything from the film's montage sequences, the newsroom politics of handling difficult sources, the newspaper industry's business models and the love of paper — was made up of "Spotlight" director Tom McCarthy and screenwriter Josh Singer, plus most of the team at the Globe that broke the story: Michael Rezendes, Sacha Pfeiffer, Walter "Robby" Robinson, Ben Bradlee Jr. and Marty Baron, who is now executive editor of The Washington Post.

As Simon pointed out early on in the discussion, it can be challenging to depict the grunt work of journalism in a way that makes good cinema. But the film's depiction of Boston's cramped interiors and expansive exteriors, all framed by looming Catholic churches, towers and properties, sandwich a drama that communicates the thrill of chasing a story: knocking on doors, searching through stacks, connecting the dots and racing the clock. When Rezendes begins writing his story weeks before publication, the top of his computer has a deadline clock that shows exactly how much time he has to finish the story.

A key conflict among the journalists is when to go to press and whether they can afford to hold their story at a time when crucial evidence was available, rather suddenly, to the public. What Simon called the "exhausting" process of continuing to report, of waiting for bigger game and not just chasing the easy target in a story, is the crux of most of his own work. It's seen particularly throughout the police investigation in "The Wire," but it runs as a thread through most all of his work — staying focused on the system, being patient, lets leads run their course. "It makes journalism an adult game," he said.

The process, a key part of Baron's charge to the Globe staff, even played out a bit in the making of the movie, according to the filmmakers. A major reveal at the end was actually discovered by Singer after McCarthy insisted they meet with one of the story's real-life principals, even though such a meeting was a long-shot to provide anything worthwhile. (To give it away would not do justice to the movie.)

McCarthy, who starred as reporter Scott Templeton in the fifth season of "The Wire," said he owed a lot to working with Simon.

"Simon taught me a lot. It was a teachable moment for me in the acting world, which doesn't always happen. And he taught me a great appreciation for journalism and journalists," McCarthy told Roll Call before the screening of his experience working with Simon and the relationship that has continued.

For those gathered Wednesday night, Simon's enthusiasm was obvious, and contagious.

"My wife is a former reporter, [and] when it gets weird, we tie each other up and read each other's clips," Simon said.

How someone reacts to that statement should quickly separate those who will love the movie and those who won't.